The disclosed invention is directed generally to a variable capacitance structure, and more particularly to a pulse width modulated switch variable capacitance structure.
Switch variable capacitor circuits have been utilized in resonant power supplies for regulation of the output voltage. A known switch variable capacitor circuit is disclosed in "Controlled Resonant Converters with Switching Frequency Fixed", Harada et al., IEEE Power Electronics Specialists Conference (PESC), 1987, pages 431-438, IEEE Catalog No. 87CH2459-6. The switch variable capacitor circuit of Harada et al. employs a variable phase drive signal to create a proportional change in effective capacitance, and includes a synchronizer, an error amplifier, a driver, and phase shifter circuits. A consideration with such circuit is that at switching frequencies above 1 MHz, phase shifter circuits are large and costly, and cannot be conveniently implemented with a single existing integrated circuit.